A cured transparent rubber composition is a material which is tough while exhibiting rubber behaviour and through which visible light passes, which for many applications is a desirable property. Applications wherein cured transparent rubber compositions may be used include, but not limited to, tubes, medical stoppers, catheters, dental dams and other medical applications, clothes and underclothes, mask, rain gear, eyewear, toys, damping materials, building components, coating material for wiring, packaging materials, protection members for computers, computer peripherals, contraceptive devices, sex toys, artificial nipples, disposable diapers, stationery, containers, food trays, balls for sports, ball chairs, protective films, seals, key covers and the like. Medical applications and similar applications are of particular interest, provided the minimum requirements with respect to transparency and mechanical properties met.
Thus, a transparent article should be clear and transparent (i.e., total transmittance greater than 80%, with haze below 30%, both according to ASTM D1003-13), and at the same time also have strong mechanical properties, i.e., tear strength greater than 23 kNm, according to ASTM D624, tensile strength greater than 13 MPa and an elongation at break greater than 1000%, both according to ISO 37:2005 (>13), good UV stability, and excellent shelf life as unvulcanised compound.
From WO2013025440 a latex is known, comprising a styrenic block copolymer and a vulcanising agent, as well as a styrenic block copolymer that is particularly suitable for use in such a latex.
WO2004104095 relates to a blend of elastomeric and thermoplastic monovinylidene aromatic-conjugated diene block copolymers, which form transparent elastomeric products.
From EP2848650 a block copolymer composition with a good balance of physical properties suitable for various types of packaging is known.
Excellent transparent rubber compositions have for instance been described in WO2014132718. Even though in this application an improved balance has been found between rubber properties such as hardness and strength on the one hand and transparency on the other hand, there is still a need for further improvement. These improved mechanical properties are particularly important for medical applications and the like. Now a new composition has been found that can be used for medical applications and other applications.